GB1037220A - Improvements in or relating to fluid pressure braking systems - Google Patents

Abstract

1,037,220. Fluid-pressure brakes. BENDIX-WESTINGHOUSE AUTOMOTIVE AIR BRAKE CO. Dec. 18, 1964 [Dec. 19, 1963], No. 51666/64. Heading F2F. In a tractor-trailer braking system including service and emergency lines, brake actuators 54 on the tractor include a spring-applied brake lock 68 for locking the actuator in a brake applied position and fluid-pressure operated means for releasing the brake lock. When a manually actuated control valve 78 is operated to the " release " position fluid flows from a parking reservoir 92 via lines 90 and 88 through the valve 78 to an outlet port 76 connected with the brake release means via lines 74 and 72 to disrupt communication between the outlet port 76 and an exhaust port leading to atmosphere. Movement of the operating lever of the control valve 78 to the " apply " position shuts off the supply of fluid to the fluid pressure released brake lock 68 and allows air in that circuit to escape to atmosphere via ports in the valve body controlling the flow through the outlet port 76 at the same time another check valve in the control valve 78 is open to allow air to pass via lines 84 and 82 to admit fluid to an emergency port 80 to apply the brakes by an emergency diaphragm 60 of each brake actuator 54. A service diaphragm 58 of each brake actuator 54 is adapted to be actuated by fluid pressure supply via conduit 50 from a quick release valve 46 and under the control of a driver's brake valve 10. Lines 32 from the brake valve 10 lead to the service port of a tractor protection valve 34 which includes at its upper end a control port 35 leading to a control chamber which receives pressure by way of a conduit 36 from a vent valve 148 which allows air to pass from conduits 14 and 18 via a two-way valve 20 and conduit 24 when the vent valve element 156 is lifted off its seat and the vent valve element 158 is seated by means of pressure supplied from lines 74 and 146. So long as conduits 74 and 146 are charged and the tractor brakes are thereby released, the trailer brakes can be controlled independently of the tractor brakes by operation of a handle 22 of a twoway control valve. When the handle 22 is moved to the left the control port 35 of the valve 34 is exhausted to atmosphere via aperture 26 and the trailer brakes are automatically applied. When the manually applied operating lever 104 of the valve 78 is released it automatically returns to the intermediate solid line " hold " position where the inlet port 88 is disconnected from the outlet port 86 and the latter is connected to atmosphere to release the air from the emergency diaphragm 60 so that the brakes are now locked in a parked position with no air in the actuator. When the lever 104 is in the " hold " position both check valves are closed and both outlet ports are connected to atmosphere. After the vehicle has been parked by movement of the lever 104 to the " apply " position as soon as the operator releases the lever it is automatically returned to the " hold " position in order that the operator may be informed as to whether or not the brakes are locked on before leaving the vehicle. The vent valve 148 enables the brakes of the trailer to be independently applied or released whenever the tractor brakes are released but positively prevent release of the trailer brakes when the tractor brakes are locked in the applied position. Whenever the tractor brakes are locked in an apply position the trailer brakes cannot be released by operation of controls readily available to the vehicle operator. Whenever the tractor brakes are released and pressure exists in the conduit 146 so that the vent valve elements 156, 158 are in their raised position, the trailer brakes may be applied and released in a normal manner independently of the tractor brakes by operation of the two-way valve 20.